The broad, long-term objectives of this research are to obtain information on the enzyme glucosamine synthase which is involved in fungal cell wall biosynthesis and is a potential target for development of agents to treat fungal infectious diseases. The objectives of this proposal are focused on the fungal opportunistic pathogen Candida albicans which causes infections in more than 90 percent of persons with AIDS and is a major problem for others whose immune system is suppressed by cancer chemotherapeutic agents or immunosuppressives used in organ transplants. The enzyme glucosamine synthase, L-glutamine:D-fructose-6-phosphate aminotransferase, (EC2.6.1.16), is an established target for antifungal drug development. The enzyme may be expressed as different isozymes in the blastoconidial and hyphal forms of Candida. The specific aims of this research are: 1. To clone the gene for glucosamine synthase from Candida albicans by either oligonucleotide probe hybridization of a C. albicans cDNA library contained in the phage Lambda-ZAP or in C. albicans genomic libraries in the yeast-Escherichia coli shuttle vectors YEp13 or pEMBLY23; or by complementation in a Saccharomyces cerevisiae glucosamine auxotroph using the same genomic libraries; 2. to sequence the glucosamine synthase gene by the Sanger dideoxy nucleotide sequencing method; 3. to probe Candida genomic DNA Southern blots with DNA probes generated from the cloned glucosamine gene to determine if there is evidence at the genomic level supporting claims of glucosamine synthase isozymes in Candida; and 4. to overexpress in Saccharomyces the enzyme coded by the Candida glucosamine synthase gene using an expression vector such as pGPD and purify the enzyme for use in antifungal drug design.